gtk3 a11y: Use correct index when deselecting child

The AT-SPI selection interface provides two functions
to unselect:

gboolean atspi_selection_deselect_selected_child (AtspiSelection *obj, gint selected_child_index, GError **error);
gboolean atspi_selection_deselect_child (AtspiSelection *obj, gint child_index, GError **error);

For the first one, 'atspi_selection_deselect_selected_child',
"child_index is the index in the selected-children list,
not the index in the parent container." [1]

For the second one, 'atspi_selection_deselect_child',
"child_index is the index of the child in the parent container". [2]

ATKSelection, on the other hand, only has

gboolean
atk_selection_remove_selection (AtkSelection *selection,
gint i);

where the index 'i' is "a gint specifying the index in the selection set.
(e.g. the ith selection as opposed to the ith child)." [3]

That means, the meaning of the index in
'atk_selection_remove_selection' is the same as in
'atspi_selection_deselect_selected_child', while
'XAccessibleSelection::deselectAccessibleChild' expects
an index in the parent container, not in the selection
set.

Therefore, convert the index from an index in the
selection to a child index first before passing
it into 'XAccessibleSelection::deselectAccessibleChild'.

(For ATK, the mapping from the two AT-SPI to the
ATK function is done in libatk-bridge.)

Example to reproduce wrong behaviour without this
change in place:

1) select cells B1 to E5 in Calc
2) start Accerciser
3) select the Calc table in Accerciser
4) get AT-SPI selection interface for the table by typing the following
in the IPython Console in Accerciser:

sel = acc.querySelection()

5) check whether child 0 (i.e. cell A1) is selected

In : sel.isChildSelected(0)
Out: False

-> OK

6) check whether child 1 (i.e. cell B1) is selected:

In : sel.isChildSelected(1)
Out: True

-> OK

7a) try to unselect cell B1:
In : sel.deselectChild(1)
Out: True

-> NOK: selection remains unchanged, cell B1 is still selected

Alternatively, intead of step 7a:
7b) try to unselect cell C1 (2nd item in the selection):

In : sel.deselectSelectedChild(1)
Out: True

-> NOK: cell B1 gets unselected instead of C1

[1] https://developer-old.gnome.org/libatspi/unstable/libatspi-atspi-selection.html#atspi-selection-deselect-selected-child
[2] https://developer-old.gnome.org/libatspi/unstable/libatspi-atspi-selection.html#atspi-selection-deselect-child
[3] https://gnome.pages.gitlab.gnome.org/atk/AtkSelection.html#atk-selection-remove-selection

Change-Id: I3c63c647e61baaa6288ffd545d8d89d8b94231de
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/124329
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 7 insertions, 1 deletions

diff --git a/vcl/unx/gtk3/a11y/atkselection.cxx b/vcl/unx/gtk3/a11y/atkselection.cxx
index 91759e8d0b21..22d515f1b6fa 100644
--- a/vcl/unx/gtk3/a11y/atkselection.cxx
+++ b/vcl/unx/gtk3/a11y/atkselection.cxx
@@ -141,7 +141,13 @@ selection_remove_selection( AtkSelection *selection,
             = getSelection( selection );
         if( pSelection.is() )
         {
-            pSelection->deselectAccessibleChild( i );
+            css::uno::Reference<css::accessibility::XAccessible> xAcc = pSelection->getSelectedAccessibleChild(i);
+            if (!xAcc.is())
+                return false;
+
+            css::uno::Reference<css::accessibility::XAccessibleContext> xAccContext = xAcc->getAccessibleContext();
+            const sal_Int32 nChildIndex = xAccContext->getAccessibleIndexInParent();
+            pSelection->deselectAccessibleChild(nChildIndex);
             return true;
         }
     }